Internal combustion engine

ABSTRACT

An internal combustion engine according to the present invention includes an exhaust treatment device provided in an exhaust passage and a burner device provided upstream of the exhaust treatment device to raise exhaust temperature. The burner device includes a fuel addition valve configured to add fuel into the exhaust passage, a first ignition device configured to ignite the added fuel, a burner catalyst provided downstream of the first ignition device, and a second ignition device provided downstream of the burner catalyst. The burner catalyst partitions the exhaust passage into an infra-catalyst passage formed inside the burner catalyst and an extra-catalyst passage formed outside the burner catalyst. The second ignition means is positioned between the extra-catalyst passage and the exhaust treatment device. Generated soot can be combusted by the second ignition device.

TECHNICAL FIELD

The present invention relates to an internal combustion engine, and inparticular, to an internal combustion engine with a burner deviceprovided upstream of an exhaust treatment device in an exhaust passageto raise exhaust temperature.

BACKGROUND ART

In an exhaust passage of an internal combustion engine, a burner devicemay be provided upstream of an exhaust treatment device (catalyst or thelike) so that heating gas generated by the burner device can be utilizedto raise exhaust temperature to heat the exhaust treatment device, thuspromoting warm-up of the exhaust treatment device. The burner devicetypically allows appropriate ignition means to ignite and combust fueladded, into the exhaust passage. Furthermore, the burner device mayinclude a burner catalyst located downstream of the ignition means tooxidize added, fuel.

Patent Document 1 discloses that a small-sized oxidation catalyst and afuel supply valve are arranged upstream of an exhaust purificationcatalyst so that when fuel is supplied to the small-sized oxidationcatalyst via the fuel supply valve, part of the supplied fuel is allowedto flow into the exhaust purification catalyst through the side of thesmall oxidation catalyst.

In the burner device, for example, inappropriate mixture of added fueland exhaust gas (particularly oxygen contained in the exhaust gas) maycause incomplete combustion, or a misfire, resulting in a relativelylarge amount of soot. If no measures are taken against such soot,various problems may occur such as blockage, of the exhaust treatmentdevice, located downstream of the burner device.

Thus, an object of the present invention is to provide an internalcombustion engine with a burner device that enables the amount of sootdischarged to be suppressed.

Citation List Patent Literature

PTL 1: Japanese Patent Laid-Open No. 2009-156164

SUMMARY OF THE INVENTION

An aspect of the present invention provides an internal combustionengine comprising an exhaust treatment device provided in an exhaustpassage and a burner device provided upstream of the exhaust treatment,device to raise exhaust temperature, the internal combustion enginebeing characterized in that:

the burner device includes a fuel addition valve configured to add fuelinto the exhaust passage, first ignition means for igniting the fueladded through the fuel addition valve, a burner catalyst provideddownstream of the first ignition means, and second ignition meansprovided downstream of the burner catalyst,

the burner catalyst is formed to occupy a part of a cross section of theexhaust passage, thus partitioning the exhaust passage into anintra-catalyst passage formed inside the burner catalyst and anextra-catalyst passage formed outside the burner catalyst, and

the second ignition means is positioned between the extra-catalystpassage and the exhaust treatment device in an axial direction of theexhaust passage.

According to this aspect, even it soot is generated by insufficientignition by the first ignition means, exhaust gas containing the soot,can be re-ignited and combusted by the second ignition means. Hence, theamount, of soot discharged from the burner device can be suppressed.

Preferably, the second ignition means is positioned near an outlet ofthe extra-catalyst passage.

Preferably, the second ignition means is positioned inside an extendedarea obtained by extending the extra-catalyst passage downstream alongthe axial direction of the exhaust passage.

Preferably, the burner catalyst is formed to contact an innercircumferential surface of the exhaust passage and includes at least onethrough-hole penetrating the burner catalyst in the axial direction ofthe exhaust passage, and the through-hole forms the extra-catalystpassage.

Preferably, the at least one through-hole is formed in a central portionof the burner catalyst, and the burner device is thus annularly formed.

Preferably, a plurality of the through-holes are formed at respectivepredetermined positions of the burner catalyst.

Preferably, the burner catalyst is positioned at a distance from theinner circumferential surface of the exhaust passage, and the annularextra-catalyst passage is formed radially outside the burner catalyst.

Preferably, the internal combustion engine comprises acquisition meansfor acquiring a temperature of the exhaust processing device, andcontrol means for controlling the fuel addition valve, the first,ignition means, and the second ignition means based on the temperatureacquired by the acquisition means, and the control means activates thefuel addition valve, the first ignition means, and the second ignitionmeans when the acquired temperature is within a predetermined firsttemperature range, and activates the fuel addition valve and the secondignition means while inactivating the first ignition means when theacquired temperature is within a predetermined second temperature rangehigher than the first temperature range.

Preferably, the exhaust treatment device comprises an oxidationcatalyst.

The present invention is very effective for suppressing the amount ofsoot discharged from the burner device.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic side view of an internal combustion engineaccording to an embodiment of the present invention;

FIG. 2 is a vertically sectional side view showing a burner device;

FIG. 3 is a vertically sectional front view of the burner device as seenfrom an upstream side;

FIG. 4 is a time chart illustrating variation in the temperature of anoxidation catalyst and in engine rotation speed which variation isobserved after cold start;

FIG. 5 is a flowchart for control of the burner device;

FIG. 6 is a vertically sectional side view of a first modification;

FIG. 7 is a vertically sectional front, view of the first modification;

FIG. 8 is a vertically sectional side view of a second modification; and

FIG. 9 is a vertically sectional front view of the second modification.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of the present invention will be described belowin detail. However, the embodiments of the present invention are notlimited to those described below. It should be noted that the presentinvention includes any variations and applications embraced by theconcepts of the present invention defined by the claims. The sizes,materials, shapes, relative arrangements, and the like of the componentsdescribed in the embodiments are not intended to limit the technicalscope of the present invention to those unless otherwise specified.

FIG. 1 schematically shows the configuration of an engine main body 1and an intake and exhaust system according to an embodiment, The enginemain body 1 forms a four-cylinder, four-cycle diesel engine mounted in avehicle. An intake pipe 2 and an exhaust pipe 3 are connected to theengine main body 1. The intake pipe 2 and the exhaust pipe 3 define anintake passage and an exhaust passage, respectively. An air flowmeter 4is provided in the middle of the intake pipe 2 to output a signalcorresponding to the flow rate of intake air flowing through the intakepipe 2. The air flow meter detects the amount of intake air flowing intothe engine main body 1 per unit time (that is, the intake flow rate).The engine main body 1 includes a plurality of cylinders each with anintra-cylinder fuel injection valve 9. However, FIG. 1 shows only asingle intra-cylinder fuel injection valve 9.

A terminal of the exhaust pipe 3 is connected to a muffler (not shown inthe drawings). The exhaust is open to the air at an outlet of themuffler. An oxidation catalyst 6 and a particulate filter (DPF) 26 arearranged in series in this order from the upstream side.

The oxidation catalyst 6 allows unearned components such as HC and CO toreact with)) O₂ to obtain CO, CO₂, H₂O, and the like. For example,Pt/CeO₂/Mn/CeO₂, Fe/CeO₂, Ni/CeO₂, or Cu/CeO₂ may be used as a catalystmaterial. The DPF 26 is configured to collect particulates (PM) such assoot in exhaust gas. The DPF 26 in the present embodiment carries acatalyst formed of rare metal and is a continuous recovery type thatenables collected particulates to be continuously oxidized andcombusted,

In addition, to the oxidation catalyst 6 and the DPF 26, an NOx catalystis preferably provided to purify NOx (nitrogen oxide) in the exhaustgas. Preferably, the NOx catalyst is arranged downstream of the DPF 26.in a spark, ignited internal combustion engine (gasoline engine), aternary catalyst is preferably provided in the exhaust passage. Theoxidation catalyst 6, the DPF 26, the NOx catalyst, and the ternarycatalyst correspond to an exhaust treatment device according to thepresent invention.

The NOx catalyst may be a NOx storage reduction (NSR) catalyst. In thiscase, the NOx catalyst functions to store NOx when inflow exhaust gashas a high concentration of oxygen and to reduce the stored NOx when theinflow exhaust gas a low concentration of oxygen and when a reductioncomponent (for example, HC) is present. The NOx catalyst includes a basematerial formed of an oxide such as alumina Al₂O₃ and containing raremetal such as platinum Pt and an NOx absorption component both carriedon the surface thereof; the rare metal serves as a catalytic component.The NOx absorption component is formed of at least one componentselected from a group including, for example, alkali metal such aspotassium K, sodium Na, lithium L, and cesium Cs, alkali earth such asbarium lie and calcium Ca, and rare earth such as lanthanum La andyttrium Y. Alternatively, the NOx catalyst may be a selective catalyticreaction (SOR) NO_(x) catalyst.

A burner device 30 is arranged upstream of the oxidation catalyst 6 inthe exhaust pipe 3, The burner device 30 includes a fuel addition valve1, and a first glow plug 21 serving as first ignition means or a firstignition device. The burner device 30 also includes a burner catalyst 8and an impact plate 20. The burner device 30 further includes a second aglow plug 22 serving as second ignition means or a second ignitiondevice.

The burner device 30 is arranged downstream of a junction of exhaustmanifolds (not shown in the drawings) connected to the engine main, body1. A turbocharger may be provided downstream of the junction of theexhaust manifolds. In this case, the burner device 30 is provideddownstream of the turbocharger and upstream of the oxidation catalyst 6.

FIG. 2 and FIG. 3 show the configuration of the burner device 30 indetail. In FIG. 2, black arrows indicate the direction of flow ofexhaust gas. The upstream side is hereinafter sometimes referred as“forward”. The downstream side is hereinafter sometimes referred as“backward”.

As shown in FIG. 2 and FIG. 3, the fuel addition valve 7 can add orinject liquid fuel (light oil) F into the exhaust pipe 3. The fueladdition valve 7 includes a single injection hole 7 a. Alternatively, aplurality of injection boles may e formed.

The fuel addition valve 7 is fixed to a valve attachment boss 11 mountedon an outer surface portion of the exhaust pipe 3 by being Inserted infothe valve attachment boss 11 perpendicularly to the axial direction ofthe exhaust pipe 3. A cooling water passage 12 is defined inside thevalve attachment boss 11 so that, cooling water serving to cool fuelinside the fuel addition valve 7 flows through the cooling water passage12. The exhaust pipe 3 includes a valve hole 13 formed therein andthrough which fuel injected through the fuel addition valve 7 is passed.

The first glow plug 21 is installed such that a first heating portion 21a provided at a leading end thereof is positioned slightly downstream ofthe fuel, addition valve 7 and upstream of the burner catalyst 8. Thefirst glow plug 21 is connected to a vehicle-mounted AC power source viaa booster circuit, (not shown in the drawings). When the first glow plug21 is energized, the first heating portion 21 a of the first glow plug21 generates heat. The heat generated by the first heating portion 21 acauses the fuel F added through the fuel addition valve 7 to be ignitedto generate flames. Part of the added fuel comes into direct contactwith the first heating portion 21 a and is thus ignited, Availableignition means is another device such as a ceramic heater or a sparkplug, particularly an electrical heating or spark ignition device.

The first glow plug 21 is fixed to the first plug attachment boss 14mounted on the outer surface portion of the exhaust pipe 3, by beinginserted from the side of the exhaust pipe 3 into the first plugattachment boss 14 perpendicularly to the axial direction of the exhaustplug 3 and the axial direction of the fuel addition valve 7. The firstglow plug 21 projects into the exhaust pipe 3 through a hole in theexhaust pipe 3.

The burner catalyst 8 is provided downstream of the first glow plug 21to oxidize and reform the fuel, added through the fuel addition valve 7.The burner catalyst 8 may be an oxidation catalyst formed of, forexample, a carrier made of zeolite and carrying rhodium or the like.

The fuel F supplied to the burner catalyst 8 is oxidized thereinprovided that the burner catalyst 8 has already been activated. Theresulting oxidation reaction heat increases the temperature of theburner catalyst 8. This enables an increase in the temperature ofexhaust gas passing the burner catalyst 8.

Furthermore, the increased temperature of the burner catalyst 8 causeshydrocarbon in the fuel having a large carbon number to be decomposed,resulting in very reactive hydrocarbon with a reduced carbon number.Thus, the fuel is reformed to have an improved reactivity.

In other words, the burner catalyst 8 forms a rapid heater thatgenerates heat rapidly on one hand and forms a reformed fuel dischargerthat discharges the reformed fuel on the other hand.

The impact plate 20 is fixed by being inserted into the plug attachmentboss M and projects into the exhaust pipe 3 through a hole in theexhaust pipe 3. The impact plate 20 may be formed of a material, such asSOS which is excellent in heat resistance and impact resistance. Theimpact plate 20 in the present embodiment is rectangular. The Impactplate 20 is arranged in proximity to and slightly below the firstheating portion 21 a. The first glow plug 21 and the impact plug 20 areinserted from the side of the upper part of the exhaust pipe 3 andextended parallel to each other and linearly in a Horizontal direction.

As shown in FIG. 2 and FIG. 3, the fuel addition valve 7 injects thefuel F obliquely downward toward the first heating portion 21 a and theimpact plate 20 so as to allow the fuel the fuel F to flow slightlydownstream. The injected fuel F has a predetermined angle of spray toform a conical fuel path. The first heating portion 21 a and the impactplate 20 are arranged in the middle of the fuel path.

Part, of the added fuel F impacts the first heating portion 21 a and theimpact plate 20. The remaining part of the fuel F passes by the firstheating portion 21 a and the impact plate 20. In particular, the impactplate 20, impacted by the fuel F, promotes atomization and spraying ofthe fuel, while feeding the fuel bouncing off the impact plate 20 to thefirst heating portion 21 a, This in turn promotes the ignition of thefirst glow plug 21.

On the other hand, the fuel having passed by the first heating portion21 a and the impact plate 20 is combusted by the flames resulting fromthe ignition or introduced into the burner catalyst 8 for oxidation andreformation without being combusted.

Thus, the burner device 30 generates hot heating gas with flames. Theheating gas is mixed with supplied exhaust gas to raise the exhausttemperature. The exhaust gas with the raised temperature is fed to theoxidation catalyst 6 and the DPF 26 to promote the warm-up andactivation of thereof.

In the burner device 30 according to the present

embodiment, a second glow plug 22 is further provided downstream of theburner catalyst 8. The second, glow plug 22 is configured similarly tothe first glow plug 21 and includes a second heating portion 22 a at aleading end thereof. The second glow plug 22 is also fixed to a secondplug attachment boss 15 mounted on the outer surface portion of theexhaust pipe 3, by being inserted from the side of the exhaust pipe 3into the first plug attachment boss 14 perpendicularly to the axialdirection of the exhaust plug 3 and the axial direction of the fueladdition valve 7. The second glow plug 22 projects into the exhaust pipe3 through a hole in the exhaust pipe 3.

Now, the burner catalyst 8 will be described in further detail. Theburner catalyst 8 is formed to occupy a part of the cross section of theexhaust passage. More specifically, the burner catalyst 8 is formed tocontact the entire inner circumferential, surface 3 a of the exhaustpipe 3, The burner catalyst 8 includes one through-hole, that is, acenter hole 13 a, formed in a central portion thereof so as to penetratethe burner catalyst 8 in the axial direction of the exhaust pipe 3.Thus, the burner catalyst 8 is annularly formed and partitions theexhaust passage in the exhaust pipe 3 into infra-catalyst passages 6formed inside the burner catalyst 8 and an extra-catalyst passage 17formed outside the burner catalyst 8. The center hole 8 a is defined byan inner pipe 15 b fixed to an inner circumferential surface portion ofthe burner catalyst 8.

As shown in FIG. 3, the exhaust pipe 3 has a circular cross section. Theburner catalyst 8 has an annular or donut-shaped cross section. Theexhaust pipe 3 and the burner catalyst 8 are coaxially arranged. Theburner catalyst 8 is what is called a straight flow type including aplurality of cells extending linearly from an upstream end to adownstream end. The individual, cells form the intra-catalyst passages16.

On the other hand, as seen in FIG. 1 and FIG. 2, the second glow plug 22(particularly the second heating portion 22 a) is positioned between theextra-catalyst passage 17 and the oxidation catalyst 6 in the axialdirection of the exhaust pipe 3. In particular, the second glow plug 22is positioned near an outlet of the extra-catalyst passage 17.Furthermore, the second glow plug 22 is positioned inside an extendedarea 18 obtained by extending the extra-catalyst passage 17 downstreamalong the axial direction of the exhaust pipe 3. Thus, the secondheating portion 22 a is positioned immediately behind the extra-catalystpassage 17 as seen from the upstream side as shown in FIG. 3.

As shown in FIG. 2 and FIG. 3, the first glow plug 21 is positionedalmost at the same height as that of the uppermost portion of the burnercatalyst 8. On the other hand, the second glow plug 22 is positionedalmost at the same height as that, of the lowermost portion of thecenter hole 8 a.

As shown in FIG. 1, the engine main body 1 is provided with anelectronic control unit (hereinafter referred to as an ECU) 10configured to control, various devices in accordance with the operationstatus of the engine main body 1, a driver's request, or the like. TheECU 10 includes a CPU configured to execute various arithmeticoperations concerning engine control, a ROM in which programs and datarequired for the control are stored, a RAM in which the results ofarithmetic operations by the CPU are temporarily stored, and an I/O portthrough which signals from an external device are input and throughwhich signals are output to the external device.

The ECU 10 connects not only to the air flow meter 4 described above butalso to various sensors via electric wiring; the sensors include a crankangle sensor 24 configured to detect the crank, angle of the engine mainbody 1, an accelerator opening degree sensor 25 configured to output anelectric signal corresponding to the opening degree of an accelerator,and a temperature sensor 27 configured to detect the temperature of theoxidation catalyst 6. Output signals from the sensors are input to theECU 10. Furthermore, the ECU 10 connects to various devices via electricwiring; the devices include the intra-cylinder fuel injection valve 9,the fuel addition valve 7, the first glow plug 21, and the second glowplug 22. The devices are controlled by the ECU 10. The ECU 10 can detectthe intake air amount based on an output value from the air flow meter 4and detect an engine rotation speed based on an output value from thecrank angle sensor 24. The ECU can further detect a demand load on theengine main body 1 based on an output value from the accelerator openingdegree sensor 25.

In the present embodiment, when temperature increase control using theburner device 30 is performed, the ECU 10 appropriately activates thefuel addition valve 7, the first glow plug 21, and the second glow plug22. That is, the ECU 10 appropriately drivingly opens (turns on) thefuel addition valve 7 to allow the fuel to be appropriately injectedthrough the fuel addition valve 7. Furthermore, the ECU 10 appropriatelyenergizes (turns on) the first glow plug and the second glow plug 22 toachieve a sufficiently high temperature.

As described above, in the burner device, for example, inappropriatemixture of the added fuel and the exhaust gas (particularly the oxygencontained in the exhaust gas) may cause incomplete combustion or amisfire, resulting in a relatively large amount of soot. If no measuresare taken against such, soot, various problem a may occur such asblockage of the exhaust treatment device, located downstream.

In particular, generated soot attaches to the inner circumferentialsurface of the exhaust pipe 3 to reduce the area of the exhaust passage.Furthermore, soot deposits early on the DPF 26, causing a recoveryprocess for recovering the DPF 26 (for example, exhaust gas is madericher by allowing the fuel to be injected through the intra-cylinderfuel injection valve 9 or the fuel addition valve 7) to be frequentlycarried out. This increases fuel consumption. Moreover, the soot blocksthe oxidation catalyst 6 and the DPF 26 to increase back pressure, thusreducing engine torque.

Thus, in the present embodiment adopts a configuration described belowin order to suppress the amount of soot discharged from the burnerdevice 30.

First, the first glow plug 21 is turned on to add the fuel through thefuel addition valve 7. Then, the added fuel is ignited by the first glowplug 21 to generate flames. The flames progress in the direction of flowof exhaust gas and pass through the uppermost portion of the burnercatalyst 8 (intra-catalyst passages 16). Furthermore, the flames spreadinto the exhaust pipe 3 and then pass through the center hole 8 a(extra-catalyst passage 17) and the whole inside of the burner catalyst8 in the direction of flow of exhaust gas.

At this time, the flame passing through the center hole 8 a is fasterthan that passing through the inside of the burner catalyst 8, and theformer passes through the burner catalyst 8 faster than the latter,because pressure loss (resistance) is greater in the intra-catalystpassages 16 than in the extra-catalyst passage 17. This difference inspeed causes the flames and the exhaust gas to be stirred and mixedimmediately after the burner catalyst 8.

However, for example, inappropriate mixture of the added fuel and theexhaust gas (particularly the oxygen contained in the exhaust gas) atthe position of the first glow plug 21 may cause insufficient ignitionand flame generation in the first glow plug 21, leading to what iscalled incomplete combustion, Then, rather than the flames, exhaust gaswith soot and unburned fuel mixed therein passes through the center hole8 a at a relatively high speed and a relatively high flow rate.

Thus, turning on the second glow plug 22 allows the exhaust gas with thesoot and the unburned fuel mixed therein to be reignited and combusted.Then, the exhaust gas having passed through the inside of the burnercatalyst 8 can be reignited and similarly combusted by the flamesresulting from the combustion as well as the mixture based on thedifference in speed.

Thus, even if the ignition and flame generation by the first glow plug21 are insufficient, the second glow plug 22 enables re-ignition andre-combustion, allowing the amount of soot discharged from the burnerdevice 30 to be suppressed. Furthermore, the adverse effect of soot onthe oxidation catalyst 6, located downstream of the burner device 30,can be avoided. Moreover, the added fuel can be sufficiently combustedon the upstream side of the oxidation catalyst 6. Thus, the performanceof the burner device 30 can be improved, promoting the capability ofwarming up the oxidation catalyst 6 and the like. Additionally, theamount of HC and CO discharged to the atmosphere can be suppressed.

In this aspect, the second glow plug 22 is suitably positioned near theoutlet of the extra-catalyst passage 17. This is because the exhaust gasdischarged from the extra-catalyst passage 17 can be immediatelyignited. Furthermore, the second glow plug 22 is suitably positionedinside the extended area 18. This is because the exhaust gas dischargedfrom the extra-catalyst passage 17 tends to flow through the extendedarea 18.

In the present embodiment, the second glow plug 22 is arranged oppositethe first glow plug 21 across the center of the exhaust pipe 3 in adiametrical direction of the exhaust pipe 3. Thus, the second glow plug22 can be arranged at a location where combustion is unlikely to occurand where soot, is likely to be generated. Hence, the soot can besuitably reignited and combusted.

On the other hand, the present embodiment exerts the following effects.That is, when exhaust gas with soot and unburned fuel mixed thereinflows through the center hole 8 a at a higher flow rate than inside theburner catalyst, more soot is collected on the inner wall of the centerhole 8 a (that is, the inner circumferential surface of the inner pipe 8b) than inside the burner catalyst. However, the collected soot can becombusted by heat generated when the burner catalyst 8 becomes hot. Theburner catalyst 8 is at a high temperature of at least 800° C. when theburner device 30 is operated. Thus, when the burner catalyst 8 is atsuch a high temperature, the soot collected on the inner wall of thecenter hole 8 a can be heated and combusted. Also in this regard, theamount of soot discharged from the burner device 30 can be suppressed.

When the burner catalyst 8 is at such a high temperature, the sootcollected inside the burner catalyst 8 can be combusted by heat from theburner catalyst 8 itself.

Now, control of the burner device 30 will be described FIG. 4illustrates variation in the temperature Tc of the oxidation catalyst 6(floor temperature) and in engine rotation speed No which variation isobserved since cold start of a vehicle with the engine mounted therein.

As shown in FIG. 4, as time elapses from t0 when the engine is started,the vehicle and the engine repeat acceleration and deceleration. Thecatalyst temperature Tc generally rises. At this time, before theoxidation catalyst 6 is activated, that is, before the oxidationcatalyst 6 reaches an activating temperature, the burner device 30 isactivated.

A basic prerequisite for activation of the burner device 30 isestablishment of the conditions (1) and (2).

(1) The temperature Tc of the oxidation catalyst 6 is equal to or lowerthan a predetermined minimum activating temperature Tc3. For example,Tc3-200° C.,

(2) The engine is carrying out deceleration fuel cut (F/C) or isoperating idly.

In (2), the condition to be met is that the engine is deceleration fuelcut. This is because the exhaust gas supplied to the burner device 30has a high concentration of oxygen (only air) and can thus be easilycombusted and because at this time, the exhaust temperature is low,serving to lower the temperature Tc of the oxidation catalyst 6.Moreover, the flow rate of the exhaust gas is relatively low, makingignition relatively easy.

The other condition to be met is that the engine is operating idly. Thisis also because the exhaust gas supplied to the burner device 30 has ahigh concentration of oxygen and because the exhaust temperature is low,serving to lower the temperature Tc of the oxidation catalyst 6.Moreover, the flow rate of the exhaust gas is low, making ignition easy.

On the other hand, when the catalyst temperature T is equal to or lowerthan the minimum, activating temperature Tc3, the amount of sootgenerated tends to increase with decreasing catalyst temperature Tc andto decrease with increasing catalyst temperature Tc.

Thus, in view of this tendency, when the catalyst temperature Tc iswithin a low temperature-side predetermined first temperature rangeTc1<Tc≦Tc2, the fuel addition valve 7, the first glow plug 21, and thesecond glow plug 22 are turned on, that is, activated. Thus, the addedfuel is positively ignited and combusted by the first glow plug 21, withthe resultant soot combusted by the second glow plug 22. For example,Tc1=100° C. and Tc2=150° C.

On the other hand, when the catalyst temperature Tc is within a hightemperature-side predetermined second temperature range Tc2≦Tc≦Tc3, thefuel addition valve 7 and the second glow plug 22 are turned on, thatis, activated, while the first glow plug 21 is inactivated. Thus, theadded fuel is utilized rather for reformation in the burner catalyst 8.The added fuel is then fully oxidized and combusted by the oxidationcatalyst 6, having a larger capacity than the burner catalyst 8.Furthermore, the added fuel is ignited only by the second glow plug 22.

When the catalyst temperature Tc is lower than the first temperaturerange Tc1≦Tc≦Tc2, the fuel addition valve 7, the first glow plug 21, andthe second glow plug 22 are all turned off. This is because at thistime, no satisfactory results are obtained by activating the burnerdevice 30.

FIG. 5 Illustrates a flowchart of a routine for the

control of the burner device 30. The routine is repeatedly carried outby the ECU 10 for every predetermined arithmetic period (for example,every 16 msec).

First, in step S101, the ECU 10 determines whether or not the engine iscarrying out deceleration fuel cut (F/C). For example, the ECU 10determines that the engine Is carrying out deceleration fuel cut, forexample, when 1) an accelerator opening degree Ac detected by theaccelerator opening degree sensor 25 is indicative of a substantiallyfully open state and when 2) an engine rotation speed Ne calculatedbased on an output from the crank angle sensor 24 is slightly greaterthan a predetermined target idle rotation speed, If the result of thedetermination is Yes, the FCU 10 proceeds to step S103.

On the other hand, if the result of the determination is No, the ECU 10proceeds to S102 to determine whether or not the engine is operatingidly. If the result of the determination is Yes, the ECU 10 proceeds tostep S103. If the result of the determination is No, the ECU 10 proceedsto step S107.

In step S103, the ECU 10 determines whether or not the temperature Tc ofthe oxidation catalyst 6 detected by the temperature sensor 27 is withinthe low temperature-side first temperature range Tc1<Tc≦Tc2. If theresult of the determination is Yes, the ECU proceeds to step S104 toturn on all. of the fuel addition valve 7, the first glow plug 21, andthe second glow plug 22. Thus, the routine is ended.

On the other hand, if the result of the determination is No, the ECU 10proceeds to step S105 to determine whether or not the detected catalysttemperature Tc is within the high temperature-side second temperaturerange tc2<Tc≦Tc3. If the result of the determination is Yes, the ECUproceeds to step S106 to turn on the fuel addition valve 7 and thesecond glow plug 22, while turning off the first glow plug 21. Thus, theroutine is ended.

On the other hand, if the result of the determination is No, the ECU 10proceeds to step S107 to turn off all of the fuel addition valve 7, thefirst glow plug 21, and the second glow plug 22. That is, the burnerdevice 30 is inactivated. Thus, the routine is ended.

Now, another embodiment will be described. The same components of thepresent embodiment, as those of the above-described embodiment(hereinafter referred to as the basic embodiment) are denoted by thesame reference numerals and will not be described below. Mainlydifferences from the basic embodiment will be described below.

FIG. 6 and FIG.. 7 show a first modification. The first modification isdifferent from the basic embodiment only in the configuration of theburner catalyst and the arrangement of the second glow plug.

A burner catalyst 8A is formed to occupy a part of the cross section ofthe exhaust passage. More specifically, the burner catalyst 8A is formedto contact the entire inner circumferential surface 3 a of the exhaustpipe 3. The burner catalyst 8A includes a plurality of through-holespenetrating the burner catalyst 8A in the axial direction of the exhaustpipe 3, that is, a plurality of outer circumferential holes 8 aA at therespective plural positions. Thus, the burner catalyst 8A is partitionedinto the intra-catalyst passages 16 formed inside the burner catalyst 8Aand the extra-catalyst passages 17 formed outside the burner catalyst8A.

Four outer circumferential holes 8 aA are formed on the outercircumferential side of the burner catalyst 8A at equal intervals in acircumferential direction. The outer circumferential holes 8 aA arepositioned at a right position, a left position, a top position, and abottom position, respectively, in the burner catalyst 8 as seen in afront view shown in FIG. 7. Each of the outer circumferential holes 8 aAis defined by an inner pipe 8 bA fixed to the burner catalyst 8A so asto form an extra-catalyst passage IV. As shown in FIG. 7, the outercircumferential hole 8 aA at the top position is located immediatelybelow the heating portion 21 a. of the first glow plug 21.

On the other hand, the second glow plug 22 is arranged such that thesecond heating portion 22 a thereof is located immediately below theouter circumferential hole 8 aA at the bottom position. Thus, the secondglow plug 22 (particularly the second heating portion 22 a thereof) ispositioned between the oxidation catalyst 6 and the extra-catalystpassages 17 in the axial direction of the exhaust pipe 3 and near theoutlet of the extra-catalyst passage 17 formed of the bottom outercircumferential hole 8 aA. The second glow plug 22 is further positionedinside the extended area 18 obtained by extending the extra-catalystpassages 17 downstream along the axial direction of the exhaust pipe 3.Furthermore, the second glow plug 22 is arranged opposite the first,glow plug 21 across the center of the exhaust pipe 3 in the diametricaldirection of the exhaust pipe 3.

The effects and control, method of the first modification are similar tothose of the basic embodiment. Thus, the first modification can suitablysuppress the amount of soot discharged from the burner device 30.

FIG. 8 and FIG. 9 show a second modification. The second modification isalso different from the basic embodiment only in the configuration ofthe burner catalyst and the arrangement of the second glow plug.

A burner catalyst 8B is configured to term a double pipe with theexhaust pipe 3. The burner catalyst 8B has a diameter smaller than theinner diameter of the exhaust pipe 3. The burner catalyst 8B iscoaxially arranged in the exhaust pipe 3. Thus, the burner catalyst 8BIs positioned away from the inner circumferential surface 3 a of theexhaust pipe 3. The annular extra-catalyst passage 17 is formed radiallyoutside the burner catalyst 8 b. A cylindrical casing 8 c is fixed onthe outer circumferential surface portion of the burner catalyst 8B. Thecasing Hc is supported in the exhaust pipe 3 by a plurality of radiallyarranged stays 19.

The burner catalyst 8B includes an approach plate 23 projectingupstream. The approach plate 23 is mounted on the lower half of a frontend of the casing 8 c. The approach plate 23 projects upstream from thecasing 8 c and is thus formed like a gutter with a semicircular crosssection. Like the casing 8 c, the approach plate 23 is supported in theexhaust pipe 3 by the plurality of radially arranged stays 19. Theapproach plate 23 receives the added fuel F having passed by the firstglow plug 21 and the impact plate 20. The approach plate 23 thenintroduces and guides the added fuel F into the burner catalyst 8B,while utilizing the flow of exhaust gas.

The first heating portion 21 a of the first glow plug 21 is positionedin front of the extra-catalyst, passage 17 positioned over the uppermostportion of the burner catalyst 8B (this extra-catalyst passage 17 ishereinafter referred to as the uppermost extra-catalyst passage 17 a).On the other hand, the second heating portion 22 a of the second glowplug 22 is positioned immediately below the upper half of the burnercatalyst 8B. That is, the second heating portion 22 a of the second glowplug 22 is positioned on the same side as that of the first glow plug 21in the diametrical direction of the exhaust pipe 3 and with respect tothe center of the exhaust pipe 3. Thus, the second glow plug 22(particularly the second heating portion 22 a thereof) is positionedbetween the oxidation catalyst 6 and the extra-catalyst passages 17 inthe axial direction of the exhaust pipe 3 and near the outlet of theuppermost extra-catalyst passage 17 a.

The effects and control, method of the second, modification are similarto those of the basic embodiment. In particular, this configurationallows flames resulting from ignition of the first glow plug 21 to flowmost positively through the uppermost extra-catalyst passage 17 a.During incomplete combustion, soot also flows most positively throughthe uppermost extra-catalyst passage 17 a, On the other hand, the secondheating portion 22 a of the second glow plug 22 is positioned near theoutlet, of the uppermost extra-catalyst passage 17 a and immediatelybehind the burner catalyst 8B. hence, soot exiting the uppermostextra-catalyst passage 17 a can be positively combusted by the secondglow plug 22, also utilizing reformed fuel exiting the burner catalyst8B. Thus, the amount of soot from the burner device 30 can be suitablysuppressed.

In the second modification, t lie position of the

second glow plug 22 may be changed such that the second glow plug 22 islocated higher with the second heating portion 22 a positionedimmediately below the uppermost extra-catalyst passage 17 a. In this andany oilier case, the second heating portion 22 a of the second glow plug22 may be positioned inside; the extended area 18 obtained by extendingthe extra-catalyst passages 17 downstream along the axial direction ofthe exhaust pipe 3.

The preferred embodiments of the present invention have been describedin detail. However, in the present invention, various other embodimentsare possible. For example, in the above-described embodiments, thetemperature of the oxidation catalyst 6 serving as an exhaust treatmentdevice is detected directly by the temperature sensor 27. However, theECU 10 may estimate the temperature of the oxidation catalyst 6 based onthe engine operation status. The detection and the estimation arecollectively referred to as the “acquisition”. The above-describednumerical, values, shapes, and the like are illustrative and may beoptionally changed. For example, at least one of the burner catalyst andthe exhaust pipe may be noncircular, for example, elliptical or oval incross section. The types and arrangement sequence of the exhausttreatment devices present downstream of the burner device are optional.The application, form, and the like of the internal combustion engineare also optional. The internal combustion engine is not limited to thevehicle mounted type or the like.

The present Invention has been described specifically to some degree.However, it should be appreciated that various alterations and changesmay be made to the present invention without departing from the spiritand scope of the claimed invention. The embodiments of the present,invention are not limited to those described above but includes anymodifications and applications embraced by the concepts of the presentinvention defined by the claims thereof. Thus, the present invention,should not be interpreted in a limited manner but is applicable to anyother technique belonging to the scope of the concepts of the presentinvention.

1. An Interned combustion engine comprising an exhaust treatment deviceprovided in an exhaust passage and a burner device provided upstream ofthe exhaust treatment device to raise exhaust temperature, the internalcombustion engine being characterized in that: the burner deviceincludes a fuel addition valve configured to add fuel into the exhaustpassage, first ignition means for igniting the fuel added through thefuel addition valve, a burner catalyst provided downstream of the firstignition means, and second ignition means provided downstream of theburner catalyst, the burner catalyst is formed to occupy a part of across section of the exhaust passage, thus partitioning the exhaustpassage into an intra-catalyst passage formed inside the burner catalystand an extra-catalyst passage formed outside the burner catalyst, andthe second ignition means is positioned between the extra-catalystpassage and the exhaust treatment device in an axial direction of theexhaust passage.
 2. The internal combustion engine according to claim 1,characterized in that the second ignition means is positioned near anoutlet, of the extra-catalyst passage.
 3. The internal combustion engineaccording to claim 1 or 2, characterized in that the second ignitionmeans is positioned inside an extended area obtained by extending theextra-catalyst passage downstream along the axial direction of theexhaust passage.
 4. The internal combustion engine according to any oneof claims 1 to 3, characterized in that the burner catalyst is formed tocontact an inner circumferential surface of the exhaust passage andincludes at least one through-hole penetrating the burner catalyst inthe axial direction of the exhaust passage, and the through-hole formsthe extra-catalyst passage.
 5. The internal combustion engine accordingto claim 4, characterized in that the at least one through-hole isformed in a central portion of the burner catalyst, and the burnerdevice is thus annularly formed.
 6. The internal, combustion engineaccording to claim 4, characterized in that a plurality of thethrough-holes are formed at respective predetermined positions of theburner catalyst.
 7. The internal combustion engine according to any oneof claims 1 to 3, characterized in that the burner catalyst ispositioned at a distance from the inner circumferential surface of theexhaust passage, and the annular extra-catalyst passage is formedradially outside the burner catalyst.
 8. The internal combustion engineaccording to any one of claims 1 to 7, characterized by comprising:acquisition means for acquiring a temperature of the exhaust processingdevice; and control means for controlling the fuel addition valve, thefirst ignition moans, and the second ignition means based on thetemperature acquired by the acquisition means, and in that the controlmeans activates the fuel addition valve, the first ignition means, andthe second ignition means when the acquired temperature is within apredetermined first temperature range, and activates the fuel additionvalve and the second ignition means while inactivating the firstignition means when the acquired temperature is within a predeterminedsecond temperature range higher than the first temperature ranges. 9.The internal combustion engine according to any one of claims 1 to 8,characterized in that the exhaust treatment device comprises anoxidation catalyst.